1. Field of the Invention
The present invention relates to a headlamp device for a vehicle that has an auxiliary lamp unit for reinforcing the brightness of the side end portion of a headlamp light distribution pattern.
2. Prior Art
In general, the headlamp for a vehicle is capable of selectively switching between a low beam light distribution pattern and a high beam light distribution pattern. However, in vehicle headlamps in which the structures of these respective light distribution patterns is fixed, it is difficult to execute a beam irradiation in accordance with a proper light distribution pattern in response to the condition of a running vehicle.
Accordingly, a vehicle headlamp device that overcomes such problems was demanded, and a headlamp device that uses an auxiliary lamp unit has been proposed. The auxiliary lamp unit executes a beam irradiation in accordance with its auxiliary light distribution pattern so as to reinforce the brightness of the side end portion of the headlamp light distribution pattern formed by the beam irradiation of the headlamp unit. The auxiliary lamp unit is turned on and off in response to the vehicle running condition.
FIG. 6 shows, in a perspective manner, a light distribution pattern formed by the headlamp device described above, assuming that the vehicle is turning left.
As seen from FIG. 6, in this headlamp device, a low beam irradiation is executed by the headlamp unit in accordance with its headlamp light distribution pattern P(L)xe2x80x2 that has a horizontal cut-off line CL1xe2x80x2 and an oblique cut-off line CL2xe2x80x2, and a beam irradiation is executed by the auxiliary lamp unit in accordance with its auxiliary light distribution pattern Paxe2x80x2 so as to reinforce the brightness of the left end portion of the headlamp light distribution pattern P(L)xe2x80x2. With this headlamp device, the road surface in front of the vehicle at the time of turning left is broadly irradiated by way of simultaneously turning on the headlamp unit and the auxiliary lamp unit.
However, in the vehicle headlamp device described above, a high luminous intensity area (hot zone) HZ1xe2x80x2 of the auxiliary light distribution pattern Paxe2x80x2 is formed at a position considerably apart from a high luminous intensity area HZ(L)xe2x80x2 of the headlamp light distribution pattern P(L)xe2x80x2. Accordingly, the problem is that the portion between the high luminous intensity areas HZ(L)xe2x80x2 and HZ1xe2x80x2 on the road surface in front of the vehicle becomes relatively dark due to the contrast between the high luminous intensity areas HZ(L)xe2x80x2 and HZ1xe2x80x2. As a result, the visibility in that portion is low.
In particular, the clipping point CP on a left curve road (a point to which it is considered that the driver pay his/her attention when turning left, that is, a position of the contact point when an eye point of the driver and the road shoulder side lane mark LM are connected with a tangent line) in front of the vehicle shifts toward the high luminous intensity area HZ(L)xe2x80x2 of the headlamp light distribution pattern P(L)xe2x80x2 as shown by arrows in FIG. 6 in accordance with the increase of the vehicle speed. Thus, the problem is that the high luminous intensity area HZ1xe2x80x2 of the auxiliary light distribution pattern Paxe2x80x2 formed on the 0left front side significantly reduces the visibility of the clipping point CP at the time of turning left at a high speed.
The present invention is made in light of the problems with the conventional vehicle headlamps described above.
It is an object of the present invention to provide an improvement in a headlamp device for a vehicle that is provided with an auxiliary lamp unit which executes a beam irradiation in accordance with its auxiliary light distribution pattern so as to reinforce the brightness of the side end portion of a headlamp light distribution pattern; and in the present invention, the vehicle headlamp device sufficiently increases the visibility of the road surface in front of the vehicle at the time of turning of the vehicle.
In other words, the present invention accomplishes the above object by applying innovation to the luminous intensity distribution in an auxiliary light distribution pattern and by providing a structure capable of controlling the light.
More specifically, the above object is accomplished by a unique structure for a headlamp device for a vehicle that includes:
a headlamp unit which irradiates a beam toward a front side of a vehicle in accordance with a predetermined headlamp light distribution pattern thereof, and
an auxiliary lamp unit which irradiates a beam in accordance with an auxiliary light distribution pattern thereof so as to reinforce the brightness of a side end portion of the headlamp light distribution pattern; and in the present invention:
the high luminous intensity area of the auxiliary light distribution pattern is formed at a position closer to the high luminous intensity area of the headlamp light distribution pattern than to the center position of the auxiliary light distribution pattern, and
a light control means that varies the beam irradiation intensity of the auxiliary lamp unit is connected to the auxiliary lamp unit.
The specific structures of the xe2x80x9cheadlamp unitxe2x80x9d and the xe2x80x9cauxiliary lamp unitxe2x80x9d are not particularly limited; and, for instance, a so-called parabola type lamp device unit and a so-called projector type lamp device unit can be employed therefor. In addition, the structures of the light sources for the xe2x80x9cheadlamp unitxe2x80x9d and the xe2x80x9cauxiliary lamp unitxe2x80x9d are not particularly limited; and, for instance, a discharge light-emitting portion of a discharge bulb and a filament of an incandescent bulb such as a halogen bulb can be employed as the light sources of the headlamp unit and the auxiliary lamp unit.
Furthermore, the xe2x80x9cauxiliary lamp unitxe2x80x9d can be a lamp that reinforces the brightness of either the right or left end portions of the headlamp light distribution pattern by the auxiliary light distribution pattern formed by the beam irradiation from the auxiliary lamp unit.
The xe2x80x9cheadlamp light distribution patternxe2x80x9d refers to a light distribution pattern that carries out a function of a headlamp, and it includes a high beam light distribution pattern and a low beam light distribution pattern.
The xe2x80x9clight control meansxe2x80x9d is not particularly limited in its specific contents of variable control as long as it can vary the beam irradiation intensity of the auxiliary lamp unit.
As seen from the above, the headlamp device for a vehicle according to the present invention includes a headlamp unit, which irradiates the beam toward the front of the vehicle in accordance with its headlamp light distribution pattern, and a auxiliary lamp unit, which irradiates the beam in accordance with its auxiliary light distribution pattern so as to reinforce the brightness of the side end portion of the headlamp light distribution pattern; and in the present invention, the high luminous intensity area of the auxiliary light distribution pattern is formed at the position closer to the high luminous intensity area of the headlamp light distribution pattern than to the center position of the auxiliary light distribution pattern. Accordingly, the headlamp light distribution pattern and the auxiliary light distribution pattern are smoothly combined together, while the brightness of the side end portion of the headlamp light distribution pattern is reinforced by the auxiliary light distribution pattern of the auxiliary lamp unit.
Further, in the present invention, the light control means that varies the beam irradiation intensity of the auxiliary lamp unit is connected to the auxiliary lamp unit. Accordingly, the auxiliary light distribution pattern can be formed in response to the vehicle running condition. When the beam irradiation intensity of the auxiliary lamp unit is gradually increased by the light control means, the high luminous intensity area becomes bright at first, then the periphery gradually becomes bright, and at last the entire auxiliary light distribution pattern becomes bright. Accordingly, the headlamp light distribution pattern and the auxiliary light distribution pattern are smoothly combined together, and the brightness of the side end portion of the headlamp light distribution pattern is reinforced by the auxiliary light distribution pattern that has a required brightness.
As seen from the above, the headlamp device for a vehicle of the present invention is provided with an auxiliary lamp unit that executes the beam irradiation in accordance with its auxiliary light distribution pattern for reinforcing the brightness of the side end portion of the headlamp light distribution pattern. As a result, the visibility of the road surface in front of the running vehicle can be sufficiently increased at the time of turning.
The xe2x80x9clight control meansxe2x80x9d used in the above structure reduces the beam irradiation intensity in response to the increase of the vehicle speed.
Accordingly, the advantage is that it is possible to sufficiently irradiate a clipping point, which is positioned comparatively close and on one side of the road surface in front of the vehicle, by way of executing a beam irradiation so that the entire auxiliary light distribution pattern is formed on the road surface in front of the vehicle at the time of turning at a low speed. On the other hand, at the time of turning at a high speed, the beam irradiation is executed so that only the high luminous intensity area of the auxiliary light distribution pattern is formed on the road surface in front of the vehicle. Thus, a clipping point which is positioned close to a far center of the road surface in front of the vehicle is irradiated, while the area just before the clipping point is prevented from becoming too bright which would reduce the visibility of the clipping point.
Furthermore, in the structure of the present invention, a semi-high luminous intensity area (which is darker than the high luminous intensity area but is brighter than the other areas in the auxiliary light distribution pattern) of the auxiliary light distribution pattern is formed so as to extend obliquely downward from the high luminous intensity area of the auxiliary light distribution pattern toward a side laterally opposite the high luminous intensity area of the headlamp light distribution pattern. Accordingly, it is possible to sufficiently irradiate the clipping point even at the time of turning at a low speed and at a middle speed. It is also possible to prevent the portions other than the clipping point on the road surface in front of the vehicle from being irradiated too much which would reduce the visibility of the clipping point.
The specific structure of the xe2x80x9cauxiliary lamp unitxe2x80x9d is not particularly limited to that described above. However, when the auxiliary lamp unit has a reflector which is sectioned into a plurality of reflection surface areas, and the high luminous intensity area, the semi-high luminous intensity area and the other areas of the auxiliary light distribution pattern are formed by reflection lights from reflection surface areas which are different from each other in the reflector, then the auxiliary light distribution pattern can be easily formed with a target luminous intensity distribution.